Foundry sand core compositions and method of preparation



FOUNDRY SAND CURE COMPOSITIONS AND METHQD F PREPARATION Stuart H. Rider, Longmeadow, Thomas Anas, Springfield, and William D. Burke, West Springfield, .Mass., assignors to Monsanto Chemical Company, St. Louis, Mo., a corporation of Delaware No Drawing. Application April 5, 1954 Serial No. 421,194

Claims. (Cl. 260-173) This invention relates to foundry sand core compositions. More particularly, this invention relates to foundry sand core compositions comprising a mixture of a suitable core sand with a modified core oil binder.

It is conventional practice to prepare metal castings in molds having hardened sand core compositions positioned therein to define internal openings in the casting. Such sand cores are prepared by shaping a mixture of sand and a suitable core binder in any suitable mold such as a core box, removing the shaped mixture from the mold and hardening the same by baking. Satisfactory core binders should not interfere With the workability of the sand and should impart satisfactory green strength and bake strength to cores molded from the mixture of sand and binder. Each of these factors'are of importance in that, for example, the mixture of sand and binder is shaped in the core box only with ditficulty if it is sticky (i. e., has poor workability), this being particularly true if the core is to be shaped by a blowing process wherein the mixture of sand and binder is blown into and compacted in a core box by air pressure. Similarly, green strength and bake strength are important since the shaped core should not be readily deformable prior to or during baking and metal casting operations.

One widely used type of core binder is a drying oilcontaining binder (commonly referred to as a core oil) which is normally compounded with the core sand in conjunction with other additives, including cereals such as flour, restricted amounts of water, etc. Although core oil-containing binder compositions, generally speaking, do not impair the workability of the sand and impart satisfactory green strength and bake strength to cores molded from the mixtures of sand and binder, the use of core oils is still attendant with various disadvantages.

A major disadvantage encountered in the use of core oil-binder compositions is the relatively long baking cycle that is required to develop satisfactory bake strength in the core. Although various proposals have been advanced in an effort to solve this problem, such proposals have generally proved to be unsatisfactory in one respect or another. This problem is particularly accentuated since it is desirable to reduce baking time without materially aifecting other variables such as the workability 0f the sand-binder mixture and the green strength of the cores molded therefrom.

Accordingly, an object of the present invention is the provision of foundry sand core compositions which will develop satisfactory bake strength after a comparatively short baking cycle.

Another object is the provision of foundry sand core compositions comprising a mixture of a core sand with a modified core oil-binder composition.

A further object is the provision of a process for the preparation of foundry sand cores.

These and other objects are attained by replacing from to 50% by weight of the core oil in a core oil-binder composition with a corresponding amount by weight of a tetra-, pentaor hexamethylol melamine fully etherified 2,847,388 Patented Aug. 12, 1958 2 with a saturated aliphatic monohydric alcohol having from 1 to 6 carbon atoms, shaping the mixture to form a core and baking the core for from 30 to 45 minutes at a temperature of about 350 to 450 F.

The following examples are given in illustration and are not intended as limitations on the scope of this invention. Where parts are mentioned, they are parts by weight.

EXAMPLE I Prepare two foundry core mixes, the compositions of which are set forth in Table I, and mold a plurality of briquettes from each of the compositions in a suitable core box. In molding the briquettes, it is found that both of the mixes have good workability and that the briquettes molded therefrom have satisfactory green strength. The

green briquettes are readily stripped from the core box Table I .-C0re mixes Raw Butylated Ottawa Corn Water Linseed Hexa- Mix Sand Flour (parts) Oil methylol (parts) (parts) (parts) Melamine (parts) Table II.Average tensile strength of baked briquettes Tensile Strength, p. s. i.

Mix

Briquettes Briquettes Baked 30 Baked 60 Minutes Minutes With reference to Table II, it is seen that the briquettes prepared from the core oil-binder composition modified I with butylated hexamethylol melamine developed a satisfactory bake strength after 30 minutes of baking whereas the unmodified composition required 60 minutes of baking in order to obtain satisfactory bake strength. In other words, a 50% reduction in baking time was realized.

When Example I is repeated using either butylated tetramethylol melamine or butylated pentamethylol melamine in place of butylated hexamethylol melamine, it found that the resultant compositions have satisfactory workability and that briquettes molded therefrom have satisfactory green strength and bake strength. It is also found that, as in the case of Example I, a satisfactory bake strength is obtained after about 30 minutes of baking at 400 F.

EXAMPLE II As a further illustration of the present invention, prepare a plurality of foundry sand core mixes having the compositions set forth in Table III. Mold briquettes from the compositions and bake and test the same in accordance with the procedure set forth in Example I. The results are set forth in Table IV.

3 When preparing the briquettes, it is noted that there is no significant difference in workability from mix to mix and it is also noted that all of the molded briquettes have satisfactory green strength.

Table III.-Core mixes #60 Corn Core Mix Ottawa Flour Water Oil 1 Ether (parts) Sand (parts) (parts) (parts) (parts) 1,000 35 10 1,000 10 35 7.5 Methylated Hexamethylol melamine, 2.5. 1,000 10 35 7.5 Butylated Hexamethylol melamine, 2.5.

A typical commercial core oil comprising linseed oil modified with slower drying oils.

Table lV.-Average tensile strength of baked briquettes As the results of the foregoing tests illustrate, a 50% reduction in baking time is realized with Mixes 2 and 3 prepared in accordance with the present invention as compared with Mix No. 1 prepared from an unmodified core oil-binder composition.

Equally satisfactory results are obtained when mixes t are prepared by blending 100 parts of #60 Ottawa sand, 10 parts by weight of corn flour and 35 parts by Weight of water with a mixture of 7.5 parts by weight of the commercial core oil and 2.5 parts by Weight of methylated or hexylated tetramethylol melamine. It is found that such mixes have good workability and that briquettes molded therefrom have satisfactory green strength. When such briquettes are baked for minutes at a temperature of about 400 F. and then tested for tensile strength in accordance with the procedure set forth in Example I, it is found that there is no significant diiference in bake strength as compared with the briquettes of Mixes 2 and 3 of Example 11 which are similarly baked for 30 minutes.

The etherified methylol melamines to be used alone I or in admixture with one another in accordance with the present invention are the tetra-, pentaand hexamethylol melamines fully etherified with saturated aliphatic monohydric alcohols having from 1 to 6 carbon atoms. The etherified compounds are easily prepared by reacting tetra-, pentaor hexamethylol melamine with a large excess of an aliphatic saturated monohydric alcohol having from 1 to 6 carbon atoms, such reaction being conducted under strongly acid conditions at a temperature of about 1040 C. If desired, mixed ethers may be prepared by an interchange reaction wherein an aliphatic alcohol having 2 or more carbon atoms is added to a methylol melamine etherified with an aliphatic alcohol having a lesser number of carbon atoms while the etherified melamine is in solution in an aliphatic alcohol which also has a lesser number of carbon atoms. Thus, when buta- 1101 is added to a solution of methylated hexamethylol melamine in methanol, the butanol reacts with the methylated melamine compound, replacing the methyl groups with butyl groups. The number of groups to be replaced in this fashion is dependent on the molar ratios of the reactants so that one, several or all of the aliphatic groups originally present may be replaced by higher aliphatic groups. Representative etherified methyl melamines of the present invention include the methylated, ethylated, propylated, butylated, pentylated and A hexylated tetra-methylol melamines, pentamethylol melamines and hexamethylol melamines. As indicated, mixed ethers of tetra-, pentaor hexamethylol melamines con taining, for example, both methyl and butyl radicals or both methyl and hexyl radicals may also be used. Such etherified methylol melamines are liquid compounds of varying viscosity which are compatible with conventionally used core oils.

In accordance with the present invention, such etherified methylol melamines are used to replace a part of the core oil normally used in foundry sand core compositions. Numerous examples of core oils are known to those skilled in the art. Such core oils normally contain, as a base, a drying oil such as perilla oil, linseed oil, menhaden oil, the highly unsaturated polymers derived from cracked gasoline, etc.

When from about 20 to 50% by weight of such a core oil is replaced by an equal amount by weight of one or more of the etherified methylol melamines of the present invention and the mixture is compounded with a suitable core sand and the other conventional ingredients in the manner known to those skilled in the art, there is obtained a fast baking composition having properties otherwise equivalent to the properties of unmodified core oil-binder compositions.

Any sand suitable for use with commercial core oils may be used to prepare the cores, such as geauga float sand, New Jersey silica sand, Ottawa foundry sand, Ottawa 1 silica sand, Portage crude sand, Ohio geauga sand, Providence core sand, Wisconsin silko bank sand, etc. Such sands are preferably washed free from organic impuritie; prior to use. V

For practical purposes, it is necessary to use a minor amount of water and a cereal such as corn flour, dextrin, wheat flour, oat meal, etc. in order that molded cores may have satisfactory green strength.

Generally speaking, satisfactory foundry sand core compositions of the present invention will comprise about 1000 parts of a suitable sand, about 7-20 parts of a mixture of about 50-80% by weight of a core oil with, correspondingly, about 50-20% by weight of an etherified methylol melamine of the present invention, about 715 parts of a suitable cereal and about parts of water. Such compositions have good workability, being of particular utility in the preparation of blown cores. Cores molded fromsuch compositions have satisfactory green strength and develop satisfactory bake strength within 3045 minutes when baked at temperatures of 350-450 F. In general, a reduction in baking time of about is obtainedwith the compositions of the present invention as compared with equivalent core oil-containing compositions free from etherified methylol melamines.

What is claimed is:

l. A foundry sand core composition consisting essentially of about 1000 parts by weight of sand, about 715 parts by weight of cereal, about 35 parts by weight of water and about 7-20 parts by weight of a mixture of about 50-80% by weight of a core oil with, correspondingly, about 5020% by weight of a compound taken from the group consisting of tetra-, pentaand hexamethylol melamines fully etherified with saturated aliphatic monohydric alcohols having from 1 to 6 carbon atoms.

2. A foundry sand core composition as in claim 1 wherein the compound is a fully etherified tetramethylol melamine.

3. A foundry sand core composition as in claim 1 wherein the compound is a fully etherified pentamethylol melamine.

4. A foundry sand core composition as in claim 1 wherein the compound is a fully etherified hexamethylol melamine.

5. A foundry sand core composition as in claim 2 wherein the etherified tetramethylol melamine is methylated tetramethylol melamine.

6. A foundry sand core composition as in claim 2 wherein the etherified tetramethylol melamine is butylated tetramethylol melamine.

7. A foundry sand core composition as in claim 3 wherein the etherified pentamethylol melamine is butylated pentamethylol melamine.

8. A foundry sand core composition as in claim 4 wherein the etherified hexamethylol melamine is methylated hexarnethylol melamine.

9. A foundry sand core composition as in claim 4 wherein the etherified hexamethylol melamine is butylated hexamethylol melamine.

10. A process for preparing a foundry sand core which comprises thoroughly intermingling about 1000 parts by weight of sand with about 715 parts by weight of cereal, about 35 parts by weight of Water and about 720 parts by weight of a mixture of 50-80% by Weight of a core oil with, correspondingly, about 5020% by weight of a 6 compound taken from the group consisting of tetra-, pentaand hexamethylol melamines fully etherified with saturated aliphatic monohydric alcohols having from 1 to 6 carbon atoms, molding a core from said mixture and baking said molded core at a temperature of about 350 450 F. for about 30-45 minutes.

References Cited in the file of this patent UNITED STATES PATENTS 2,197,357 Widmer et a1 Apr. 16, 1940 2,313,672 Salzberg et a1 Mar. 9, 1943 2,433,168 Staeger Dec. 23, 1947 2,521,614 Valyi Sept. 5, 1950 2,619,476 Malinowski Nov. 25, 1952 FOREIGN PATENTS 469,660 Canada Nov. 28, 1950 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No, 2,847,388 August 12, 1958 Stuart Rider et El,

umbered patent requiring correction and that the said Letters Patent should read as corrected below.

It is hereby certified that error appears in the printed specification of the above 11 Column 2, line 59, after "it" insert is e--; column 3, line 36,, I for "100 parts" read 1000 parts lines 73 and 74, for "n'nethgrl read Signed and sealed this 11th day of November 1958,

(SEAL) Attest:

KARL RAXLINE ROBERT c. WATSON Attesting Oflicer Commissioner of Patents 

1. A FOUNDRY SAND CORE COMPOSITION CONSISTING ESSENTIALLY OF ABOUT 1000 PARTS BY WEIGHT OF SAND, ABOUT 7-15 PARTS BY WEIGHT OF CEREAL, ABOUT 35 PART BY WEIGHT OF WATER AND ABOUT 7-20 PARTS BY WEIGHT OF A MIXTURE OF ABOUT 50-80% BY WEIGHT OF A CORE OIL WITH, CORRESPONDINGLY, ABOUT 50-20% BY WEIGHT OF A COMPOUND TAKEN FROM THE GROUP CONSISTING OF TETRA-, PENTA- AND HEXAMETHYLOL MELAMINES FULLY ETHERIFIED WITH SATURATED ALIPHATIC MONOHYDRIC ALCOHOLS HAVING FROM 1 TO 6 CARBON ATOMS. 